The present invention relates to motor vehicle clutch control mechanisms in general, and more particularly to a friction clutch hydraulic control apparatus comprising a slave cylinder for operating the clutch release mechanism remotely from a master cylinder, the hydraulic control mechanism being prefilled with hydraulic fluid and pretested prior to shipment to a motor vehicle manufacturer for installation in a motor vehicle.
It is now known to prefill with hydraulic fluid a motor vehicle clutch control apparatus, comprising a master cylinder, a reservoir of fluid, and a slave cylinder for operating the throwout bearing of a mechanical diaphragm spring clutch, as disclosed in Britist Pat. No. 1,539,879 and in corresponding U.S. Pat. No. 4,407,125 and co-pending application Ser. No. 376,248, filed May 10, 1982, all assigned to the same assignee as the present application. In addition, co-pending applications Ser. Nos. 477,159, 477,160, 477,161 and 477,162, all filed Mar. 21, 1983 and assigned to the same assignee as the present application, also disclose diverse forms of prefilled hydraulic control mechanisms for motor vehicle clutches.
Prefilling with hydraulic fluid and pretesting hydraulic apparatus for operating motor vehicle mechanical clutches present the many advantages, for the motor vehicle manufacturer, of receiving a fully assembled mechanism comprising all the components filled with hydraulic fluid and pretested for proper operation, ready to install on a motor vehicle on the assembly line, without requiring that the components be installed separately, connected by way of a flexible conduit, and filled after installation with hydraulic fluid while being purged of any air contained in the apparatus.
In apparatus wherein the slave cylinder, actuating the clutch release mechanism, takes the form of a conventional cylindrical cylinder-piston assembly with the piston rod projecting from the cylinder housing attached at its end to the clutch release lever, the slave cylinder being attached at some portion of the clutch bell housing, permanent connection of the master cylinder to the slave cylinder by means of a flexible conduit, and prefill of the apparatus with hydraulic fluid do not present much inconveniences, whether the slave cylinder or the master cylinder is installed first on the vehicle, and the other cylinder installed at some other subsequent station on the assembly line. The last installed component may be simply left dangling on the end of the flexible conduit, or may be attached by means of straps, wires or strings to some portion of the motor vehicle frame or body, until definitely mounted in its operative position. However, with the present trend towards utilizing annular slave cylinders, disposed concentric to the driveshaft and bolted either to the face of the transmission or gearbox casing or, in the alternative, mounted on a side of or made integral with the clutch bell housing, such that the annular piston within the concentric annular slave cylinder may operate the clutch throwout bearing, it is difficult to provide a fully assembled, fully tested, prefilled apparatus, without some accompanying inconveniences. Such inconveniences relate to the requirement that the annular slave cylinder be installed first in the clutch bell housing, or on the transmission casing face, and the master cylinder on the end of the flexible line or conduit interconnecting the master and slave cylinders be provisionally attached, in some manner by strings, wires or straps to the motor vehicle frame, and subsequently installed in its proper position through the passenger compartment floorboard or bulkhead.